I did a 3-month internship there and saw some of the ridiculous situations others are replaying here (my favorite of which was 8am-8pm work hours every day).

I decided to not go back, but in the end having Amazon on my resume (even as an internship, as I'm relatively young) was basically a free pass to interview anywhere else I wanted. I'd say it was a shitty experience while I was there, but net positive in the long run if only because of Amazon's klout.